Robots and other computer controlled machines are widely used in manufacturing. Robots are often used, for example, to perform repetitive tasks that require a high level of precision. Robots are used on vehicle assembly lines to perform welding operations, install glass, and even install valve seats in high performance engines.
Robots are useful in many of these roles because the part involved can be precisely positioned in a repeatable manner. In other words, the robot works on the same part in the same position and thus, has a useful coordinate system to direct its movements. For a frame welding robot, for example, the frame to be welded is placed into a jig that precisely locates the frame. Thus, while the robot may have programs to weld multiple frames, the frame is nonetheless located in a jig providing a fixed coordinate system.
A problem arises, however, when the object to be machined is not in a known, fixed coordinate system, such as an aircraft sitting on the tarmac in a maintenance facility. This problem can be further exacerbated when no visible fiducials, or reference points, are available. The fuselage of an aircraft, for example, tends to be a vast expanse with few reference points with which to establish a coordinate system. Modern composite aircraft are generally manufactured in large sections and have many fewer fasteners and other reference points, for example, when compared with older, aluminum construction. This further reduces the number of available reference points.
What is needed therefore are systems and methods for accurately locating a robot in space to perform various functions. The system should use a combination of technologies to enable a robot, or other machine, to accurately locate itself on a part without the use of an absolute reference frame. It is to such systems and methods that embodiments of the present disclosure are primarily directed.